1. Field of Invention
The present invention relates to a method for forming a pattern, and a composition for forming a resist underlayer film.
2. Description of the Related Art
In producing elements of integrated circuits, a multilayer resist process has been employed nowadays in order to achieve a higher degree of integration. In brief, according to this process, a composition for a resist underlayer film is first coated on a substrate to be processed (hereinafter, merely referred to as “substrate”), thereby forming a resist underlayer film, on which a resist composition is coated to form a resist coating film, followed by transferring a mask pattern using a reduced projection exposure system (stepper), and developing with an appropriate developer to obtain a resist pattern. Subsequently, the resist pattern is transferred to the resist underlayer film by dry etching, and further the resist underlayer film pattern is transferred to the substrate by dry etching to enable a substrate having a desired pattern formed to be obtained.
In such a multilayer resist process, it is necessary to remove an underlayer film pattern remaining on the substrate, and for this purpose, a method including an ashing treatment by oxygen plasma or the like has been commonly employed (see Japanese Unexamined Patent Application, Publication No. H10-92740). However, when such an ashing treatment is carried out, disadvantages may occur such as deterioration of the surface of the substrate such as silicon, or increase in the relative permittivity in the case of substrate materials having a low relative permittivity, and the like.
In order to eliminate the foregoing disadvantages, a method for removing an underlayer film pattern in which an ashing treatment is not carried out has been desired. As such a type of method, for example, an underlayer film form material has been proposed which contains a resin component having a substituent that generates a sulfonate group upon application of a predetermined energy to remove a terminal group (see Japanese Unexamined Patent Application, Publication No. 2004-177668). According to this technique, sulfonate groups are generated on the underlayer film resin by applying the energy such as heating in forming the resist underlayer film; therefore, removal with a removing liquid after the dry etching can be carried out, whereby the necessity of the ashing treatment is obviated. However, in this case, it is necessary to elevate the temperature to 80° C. or higher during the resist underlayer film is formed, and a strong acid group that is a sulfonate group continuously exerts influences on the substrate during the dry etching; therefore, occurrence of deterioration of the surface of the substrate, and the like has not yet been overcome.